Method of radially expanding a tubular element

Abstract

A method of radially expanding a tubular element comprises inducing the wall of the tubular element to bend radially outward and in an axially reverse direction so as to form an expanded tubular section extending around an unexpanded section of the tubular element. The bending process occurs in a bending zone of the tubular element, and the method further comprises progressively increasing the length of the expanded tubular section by inducing the bending zone to move in an axial direction along the tubular element.

Description

[0001]The present application claims priority from PCT / EP2007 / 057068, filed 11 Jul. 2007, which claims priority from European Patent Application 06117170.8 filed 13 Jul. 2006.FIELD OF THE INVENTION[0002]The present invention relates to a method of radially expanding a tubular element.BACKGROUND OF THE INVENTION[0003]Expansion of tubular elements finds application in various fields of technology such as, for example the industry of oil and gas production from a wellbore formed in an earth formation. Wellbores are generally provided with one or more casings or liners to provide stability to the wellbore wall, and / or to provide zonal isolation between different earth formation layers. The terms “casing” and “liner” refer to tubular elements for supporting and stabilising the wellbore wall, whereby it is generally understood that a casing extends from surface into the wellbore and that a liner extends from a downhole location further into the wellbore. However, in the present context, t...

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Benefits of technology

[0010]Thus, the tubular element is effectively turned inside out during the bending process. The bending zone defines the location where the bending process takes place. By inducing the bending zone to move in axial direction along the tubular element it is achieved that the tubular element is progressively expanded without the need for an expander that has to be pushed, pulled or pumped through the tubular element. Furthermore the expanded tubular section retains its shape due to plastic deformation, that is permanent deformation, of the wall. It is thereby achieved that the expanded tubular section automatically maintains its expanded shape, that is, no external force or pressure needs to be exerted to the expanded tubular section to maintain its expanded shape. If, for example, the expanded tubular section has been expanded against the wellbore wall as a result of said bending of the wall, no external radial force or pressure needs to be exerted to the expanded tubular section to keep it against the wellbore wall. Suitably the wall of the tubular element is made of a metal such as steel or any other ductile metal capable of being plastically deformed by eversion of the tubular element. The expanded tubular section then has adequate collapse resistance, for example in the order of 100-150 bars. If the tubular element extends vertically in the wellbore, the weight of the remaining tubular section can be utilised to contribute to the force needed to induce downward movement of the bending zone.

[0012]In order to induce said movement of the remaining tubular section, preferably the remaining tubular section is subjected to an axially compressive force acting to induce said movement. The axially compressive force preferably at least partly results from the weight of the remaining tubular section. If necessary the weight can be supplemented by an external, downward, force applied to the remaining tubular section to induce said movement. As the length, and hence the weight, of the remaining tubular section increases, an upward force may need to be applied to the remaining tubular section to prevent uncontrolled bending or buckling in the bending zone.

[0013]If the bending zone is located at a lower end of the tubular element, whereby the remaining tubular section is axially shortened at a lower end thereof due to said movement of the bending zone, it is preferred that the remaining tubular section is axially extended at an upper end thereof in correspondence with said axial shortening at the lower end thereof. The remaining tubular section gradually shortens at its lower end due to continued reverse bending of the wall. Therefore, by extending the remaining tubular section at its upper end to compensate for shortening at its lower end, the process of reverse bending the wall can be continued until a desired length of the expanded tubular section is reached. The remaining tubular section can be extended at its upper end, for example, by connecting a tubular portion to said upper end in any suitable manner such as by welding. Alternatively, the remaining tubular section can be provided in the form of a coiled tubing which is unreeled from a reel and gradually inserted into the wellbore. Thus, the coiled tubing is extended at its upper end by unreeling from the reel.

[0014]As a result of forming the expanded tubular section around the remaining tubular section, an annular space is formed between the unexpanded and expanded tubular sections. To increase the collapse resistance of the expanded tubular section, a pressurized fluid can be inserted into the annular space. The fluid pressure can result solely from the weight of the fluid column in the annular space, or in addition also from an external pressure applied to the fluid column.

[0018]To reduce any buckling tendency of the unexpanded tubular section during the expansion process, the remaining tubular section advantageously is centralised within the expanded section by any suitable centralising means.

Problems solved by technology

As a result, the cross-sectional wellbore size available for oil and gas production decreases with depth.

Such method can lead to high friction forces that need to be overcome, between the expander and the inner surface of the tubular element.

Also, there is a risk that the expander becomes stuck in the tubular element.

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